diff --git a/Cargo.toml b/Cargo.toml
index a74c763..1aaca4a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,6 +11,7 @@ crate-type = ["cdylib", "rlib"]
 js-sys = "0.3"
 log = "0.4"
 fern = "0.6"
+html-escape = "0.2"
 screeps-game-api = "0.21"
 # If you'd like to use a locally-cloned out version of the game API crate
 # (for testing PRs, etc), you can use a local path (replacing the above line):
@@ -30,14 +31,14 @@ lto = true
 # Replace the following to enable wasm-opt optimization
 # wasm-pack will try to install wasm-opt automatically, but it must be installed by hand on some
 # operating systems.
-wasm-opt = false
+#wasm-opt = false
 # See wasm-opt for full available options; handy examples:
 # -O4 - optimize aggressively for performance
 # -Oz - optimize aggressively for code size
 # -g - leave debug info in place, allowing for more descriptive stack traces on panic
 # --disable-sign-ext - prevents opcodes that the screeps servers can't load (see 
 # https://github.com/rustyscreeps/screeps-game-api/issues/391)
-#wasm-opt = ["-O4", "--disable-sign-ext"]
+wasm-opt = ["-O4", "--signext-lowering"]
 
 [features]
 default = []
diff --git a/src/logging.rs b/src/logging.rs
index bc0916e..ea0f66e 100644
--- a/src/logging.rs
+++ b/src/logging.rs
@@ -1,6 +1,6 @@
-use core::panic::PanicInfo;
 use std::{fmt::Write, panic};
 
+use html_escape::encode_text;
 use js_sys::JsString;
 use log::*;
 use screeps::game;
@@ -39,7 +39,7 @@ pub fn setup_logging(verbosity: log::LevelFilter) {
                 "({}) {}: {}",
                 record.level(),
                 record.target(),
-                message
+                encode_text(&message.to_string())
             ))
         })
         .chain(Box::new(JsLog) as Box<dyn log::Log>)
@@ -48,7 +48,11 @@ pub fn setup_logging(verbosity: log::LevelFilter) {
                 .level(log::LevelFilter::Warn)
                 .format(|out, message, _record| {
                     let time = game::time();
-                    out.finish(format_args!("[{}] {}", time, message))
+                    out.finish(format_args!(
+                        "[{}] {}",
+                        time,
+                        encode_text(&message.to_string())
+                    ))
                 })
                 .chain(Box::new(JsNotify) as Box<dyn log::Log>),
         )
@@ -71,7 +75,7 @@ extern "C" {
     fn stack_trace_limit(size: f32);
 }
 
-fn panic_hook(info: &PanicInfo) {
+fn panic_hook(info: &panic::PanicHookInfo) {
     // import JS Error API to get backtrace info (backtraces don't work in wasm)
     // Node 8 does support this API: https://nodejs.org/docs/latest-v8.x/api/errors.html#errors_error_stack